Structural optimization of the manned pressure hull of a deep manned submersible based on a new safety standard

The most critical component of a deep manned submersible is the manned pressure hull. It provides not only a safe living space for pilots and scientists but also provides a proper working condition for non-pressure-resisting and non-water-repellent equipments. At the same time, the weight of the pressure hull occupies a large part of the total weight of the deep manned submersible. So the pressure hull should be designed to have enough strength, water-tightness and as light as possible. As the most commonly used pressure hull type, spherical pressure hull has been used in all the existing deep manned submersibles such as Alvin of USA, Nautile of France, MIR I&II, RUS and Consul of Russia, Shinkai6500 of Japan and Jiaolong of China. Facing the requirement of designing a new 4500m manned submersible, we have carried out a comparative study on the current available design rules from various classification societies. According to this comparison, significantly different results among these design rules have been found and many existing spherical pressure hulls are found not to be in compliance with most of the current design rules. Based on a systematic FEM study on the effects of various parameters on the ultimate strength of spherical shells under external pressure, a new safety standard for the design of spherical pressure hull of deep manned submersibles is proposed. In this paper, the new safety standard is first introduced and then a structural optimization of the titanium alloy spherical pressure hull of a 4500m deep manned submersible is performed based on the new safety standard. Finally, the optimal solution is presented

Exploring the dark matter inelastic frontier with 79.6 days of PandaX-II data

We report here the results of searching for inelastic scattering of dark matter (initial and final state dark matter particles differ by a small mass splitting) with nucleon with the first 79.6-day of PandaX-II data (Run 9). We set the upper limits for the spin independent WIMP-nucleon scattering cross section up to a mass splitting of 300 keV/c$^2$ at two benchmark dark matter masses of 1 and 10 TeV/c$^2$.Comment: 5 pages, 6 figure

Dark Matter Results From 54-Ton-Day Exposure of PandaX-II Experiment

We report a new search of weakly interacting massive particles (WIMPs) using the combined low background data sets in 2016 and 2017 from the PandaX-II experiment in China. The latest data set contains a new exposure of 77.1 live day, with the background reduced to a level of 0.8$\times10^{-3}$ evt/kg/day, improved by a factor of 2.5 in comparison to the previous run in 2016. No excess events were found above the expected background. With a total exposure of 5.4$\times10^4$ kg day, the most stringent upper limit on spin-independent WIMP-nucleon cross section was set for a WIMP with mass larger than 100 GeV/c$^2$, with the lowest exclusion at 8.6$\times10^{-47}$ cm$^2$ at 40 GeV/c$^2$.Comment: Supplementary materials at https://pandax.sjtu.edu.cn/articles/2nd/supplemental.pdf version 2 as accepted by PR

Chewing Gum for Intestinal Function Recovery after Colorectal Cancer Surgery: A Systematic Review and Meta-Analysis

Background. This meta-analysis was performed to assess the efficacy and safety of chewing gum in intestinal function recovery after colorectal cancer surgery. Methods. A systematic search was conducted in PubMed, Embase, Science Direct, and Cochrane library for relevant randomized controlled trials (RCTs) published until April 2017. Summary risk ratios or weighted mean differences with 95% confidence intervals were used for continuous and dichotomous outcomes, respectively. Results. 17 RCTs with a total number of 1845 patients were included. Gum chewing following colorectal cancer surgery significantly reduced the time to first passage of flatus (WMD −0.55; 95% CI −0.94 to −0.16; P=0.006), first bowel movement (WMD −0.60; 95% CI −0.87 to −0.33; P<0.0001), start feeding (WMD −1.32; 95% CI −2.18 to −0.46; P=0.003), and the length of postoperative hospital stay (WMD −0.88; 95% CI −1.59 to −0.17; P=0.01), but no obvious differences were found in postoperative nausea, vomiting, abdominal distention, pneumonia, and mortality, which were consistent with the findings of intention to treat analysis. Conclusions. Chewing gum could accelerate the recovery of intestinal function after colorectal cancer surgery. However, it confers no advantage in postoperative clinical complications. Further large-scale and high-quality RCTs should be conducted to confirm these results

Low-mass dark matter search results from full exposure of PandaX-I experiment

We report the results of a weakly-interacting massive particle (WIMP) dark matter search using the full 80.1\;live-day exposure of the first stage of the PandaX experiment (PandaX-I) located in the China Jin-Ping Underground Laboratory. The PandaX-I detector has been optimized for detecting low-mass WIMPs, achieving a photon detection efficiency of 9.6\%. With a fiducial liquid xenon target mass of 54.0\,kg, no significant excess event were found above the expected background. A profile likelihood analysis confirms our earlier finding that the PandaX-I data disfavor all positive low-mass WIMP signals reported in the literature under standard assumptions. A stringent bound on the low mass WIMP is set at WIMP mass below 10\,GeV/c$^2$, demonstrating that liquid xenon detectors can be competitive for low-mass WIMP searches.Comment: v3 as accepted by PRD. Minor update in the text in response to referee comments. Separating Fig. 11(a) and (b) into Fig. 11 and Fig. 12. Legend tweak in Fig. 9(b) and 9(c) as suggested by referee, as well as a missing legend for CRESST-II legend in Fig. 12 (now Fig. 13). Same version as submitted to PR